System and method for black silicon etching utilizing thin fluid layers

Abstract

Systems and methods for etching the surface of a substrate may utilize a thin layer of fluid to etch a substrate for improved anti-reflective properties. The substrate may be secured with a holding fixture that is capable of positioning the substrate. A fluid comprising an acid and an oxidizer for etching may be prepared, which may optionally include a metal catalyst. An amount of fluid necessary to form a thin layer contacting the surface of the substrate to be etched may be dispensed. The fluid may be spread into the thin layer utilizing a tray that the substrate is dipped into, a plate that is placed near the surface of the substrate to be etched, or a spray or coating device.

The invention claimed is: 
     
       1. A method for anti-reflective etching the surface of a substrate, the method comprising:
 securing the substrate with a holding fixture, wherein the holding fixture controls positioning of the substrate; 
 preparing a fluid, wherein the fluid comprises an acid and an oxidizer; 
 dispensing the fluid, wherein the fluid is dispensed into a tray, and the fluid contacts the substrate after being dispensed; 
 spreading the fluid onto the substrate into a thin layer with a thickness of 5 mm or less, wherein the fluid is dispersed into the thin layer with the thickness by positioning the first surface of the substrate a predetermined distance from a bottom surface of the tray without submerging the substrate in the fluid, the fluid is spread by moving the substrate into the tray, moving the tray toward the substrate, or a combination thereof, the substrate enters the fluid at an angle of 20 to 60 degrees, the thin layer contacts a first surface of the substrate for a predetermined time, and the thickness of the fluid is controlled by controlling a separation distance between the first surface of the substrate and an opposing surface of a dispersion mechanism opposite the first surface, and the fluid is not in contact with a second surface of the substrate opposite the first surface; and 
 removing the thin layer of fluid from the substrate, wherein the first surface of the substrate has reduced reflectivity. 
 
     
     
       2. The method of  claim 1 , wherein a metal catalyst is deposited on the substrate prior to the anti-reflective etching. 
     
     
       3. The method of  claim 1 , further comprising:
 preparing a deposition fluid, wherein the deposition fluid comprises a metal catalyst; 
 dispensing the deposition fluid, wherein the deposition fluid contacts the substrate after being dispensed; 
 spreading the deposition fluid onto the substrate into a deposition layer, wherein the deposition layer contacts the first surface of the substrate for a predetermined deposition time; and 
 removing the deposition layer of deposition fluid from the substrate, wherein the metal catalyst is deposited on portions of the substrate. 
 
     
     
       4. The method of  claim 1 , wherein the fluid further comprises a metal catalyst. 
     
     
       5. The method of  claim 1 , wherein components of the fluid are mixed in an inline manner in a conduit prior to the dispensing step. 
     
     
       6. The method of  claim 1 , wherein the fluid remains in contact with the substrate for 10 second to 5 minutes. 
     
     
       7. The method of  claim 1 , wherein the fluid is dispensed by capillary forces. 
     
     
       8. The method of  claim 1 , wherein the substrate is masked prior to the anti-reflective etching.